Conventional circuitry employed for power inverter/ converters include a monolithic pulse-width modulator (PWM) integrated circuit that drive a push-pull pair of mosfet transistors which alternately pulse a high-current DC power source into the primary of a ferrite transformer at a high switching frequency. The transformer output is rectified with a full-wave bridge of ultra-fast rectifiers. A PWM typically looks for a steady DC reference voltage at its input to emulate that particular waveshape.
Prior applications have either designed an inverter/ converter using a PWM to eliminate the DC component of a high switching frequency wave signal, or require more than one DC voltage source to obtain a multi-phase AC power signal. For example, the Rhodes et al. U.S. Pat. No. 4,939,633 is directed to an inverter power supply system that includes a PWM circuit design that can eliminate the DC component from the high frequency AC component from the output waveform to produce a 60 hertz/120 volt AC output. This design is limited, however, to replicating a waveform that cannot include a DC component. Further, the Rhodes et al. '633 circuit would require a heavier and larger transformer to raise or lower the voltage than one operating at a switching frequency of 100 kilohertz.
Another example is the Glennon U.S. Pat. No. 4,502,106, which is directed to a circuit using a PWM to obtain a multi-phase AC power signal. This circuit requires the use of two DC voltage sources and lacks the ability to send a feedback signal to increase or decrease the voltage at the PWM to adjust the pulse width of the DC power source in response to the feedback signal.
It has been discovered in accordance with the invention described below that instead of just relying on a stable DC reference voltage on the PWM, a precision-rectified, low voltage sample of a desired wave-shape source can be used as a controlling signal to adjust the PWM to replicate any desired wave-shape. By selecting complimentary filter components after rectification at the output of the secondary of the transformer, the PWM can adjust to any rapidly-changing wave-shape.